1. Field of the Invention
The present invention relates to a method of discriminating the type of recording medium and, more specifically, to a method of discriminating a recording medium associated with a recording system and the structure of the same.
2. Description of the Related Art
Various types of recording medium are used in a recording system as typified by a laser-beam printer or an inkjet printer, such as normal paper, glossy paper, coated paper, or plastic film for an overhead projector (OHP). In order to record images of optimum quality for various types of recording medium, it is necessary to set various parameters, which correspond to the type of recording medium, to a printer when recording.
A case of an inkjet printer will be described for example. When normal paper and coated paper are compared, the coated paper can absorb and contain more ink than the normal paper. As such, the recording parameters are set to provide a larger amount of ink or a higher number of times of ink injection for the coated paper. It is because images can be formed in brighter colors on the recording medium by injecting a larger amount of ink. Since glossy paper used for recording picture-level images can absorb still larger amount of ink than the coated paper, the recording system can create an image with high level of quality with the settings for changing the overlapping ways of ink colors and the amount of ink injection (injection amount) or the number of times of ink injection.
The parameters which are changed according to the type of recording medium are generally set via a printer driver installed on a host computer based on the type of recording medium or a recording mode (recording quality) specified by a user before recording. The printer driver generates recording data for enabling recording corresponding to the type of recording medium or the recording mode specified by the user. Then, the recording system forms an image of a recording quality specified by the user based on the generated recording data.
However, in a case where the user specifies a type of recording medium different from the actual type because he/she does not have knowledge of, or misjudges, the type of recording medium, the recording system performs recording corresponding to the type of recording medium specified by the user. Therefore, optimum recording corresponding to the recording medium is not achieved.
In order to solve the above-described problem, there is a method for discriminating the type of recording medium by irradiating light onto the recording medium and discriminating the type of recording medium according to differences in quantity of light reflected from the recording medium.
As shown in FIG. 10, Japanese Patent Laid-Open No. 2000-301805 (U.S. Pat. No. 6,291,826) discloses a method of determining the property of the surface and the precise structure of the medium based on the quantity of light reflected or transmitted when light is irradiated on the recording medium from one or more directions and, based on judged result, discriminating whether it is normal paper, coated paper, photographic paper, or transparent film (OHP plastic film).
In FIG. 10, reference numeral 1010 designates a recording medium, reference numerals 1012, 1014, 1016 designate light sources for irradiating light to the recording medium from different angles respectively, and reference numeral 1022 designates a sensor for receiving transmitted light or reflected light from the light irradiated from the light sources 1012, 1014, 1016.
However, in the method disclosed in Japanese Patent Laid-Open No. 2000-301805, it is necessary to provide the light sources for irradiating light respectively from different directions.
According to the structure disclosed in the above-described Patent Document, a light source which emits a visible light beam, such as a light-emitting diode, an incandescent lamp, a laser diode, a surface light-emitting diode, is employed. A photoelectric sensor such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) is used as a sensor for receiving the transmitted light or the reflected light, in order to determine the difference in reflecting property on the surface of the recording medium and the precise structure on the surface of the recording medium, thereby the type of the recording medium can be discriminated. At this time, reflected light originating from the light source 1014 is detected via a low-resolution optical device system with a large depth of field for the normal paper, reflected light originating from the light source 1016 is detected by a high magnification for the photographic paper, reflected light originating from the light source 1014 is detected by a magnification at a certain level, and transmitted light originating from the light source 1012 is detected for the OHP plastic film.
In this manner, in order to discriminate the various types of recording medium, an apparatus having a complex structure which includes a mechanism for changing the incident angle of the light sources and changing the detection magnifications of the reflected light and the transmitted light is required.
Moreover, since the reflecting properties of normal paper and coated paper are similar, there is a risk of misdiscrimination. However, in the inkjet printer, since the recording method (parameters to be set when recording) is different between the normal paper and the coated paper, it is desirable that such discrimination is performed accurately also between the normal paper and the coated paper.